Dual Activator-Support Catalysts for Ethylene Long-Chain Branch Control
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Solution Overview
Problem
Existing metallocene-based catalyst systems for producing olefin-based polymers face challenges in adjusting long chain branch (LCB) content without significantly affecting other polymer properties, such as melt index and molecular weight distribution, by simply substituting metallocene compounds.
Innovation Solution
A catalyst composition comprising a metallocene compound, an organoaluminum compound, a high LCB activator-support, and a low LCB activator-support is used, allowing control of LCB content by adjusting the relative amounts of these components, specifically utilizing fluorided and sulfated solid oxides like fluorided silica-coated alumina and sulfated bentonite.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If one metallocene compound is substituted for another to increase or decrease long chain branching, then the LCB content is adjusted, but many other polymer properties such as melt index, molecular weight distribution, and short chain branching are drastically affected
Solution Approach 1:
The invention divides the catalyst system into separate functional components: a metallocene compound for controlling polymerization activity and a co-catalyst system (comprising a main salt and an activator) for controlling LCB content. This segmentation allows independent optimization of each component's function, enabling precise LCB control without affecting other polymer properties controlled by the metallocene structure.
Solution Approach 2:
The co-catalyst system acts as an intermediary between the metallocene compound and the olefin monomer. By introducing this intermediate component, the invention decouples the relationship between metallocene structure and LCB content, allowing LCB control through co-catalyst selection rather than metallocene substitution, thereby maintaining polymer property stability.
2Manufacturing precision
If the metallocene component is replaced to control LCB content, then the desired LCB level is achieved, but the complexity of catalyst system optimization increases
Solution Approach 1:
The invention extracts the LCB control function from the metallocene component and places it in the co-catalyst system. This extraction simplifies the overall system by allowing the metallocene compound to remain constant while only the co-catalyst needs to be adjusted for LCB control, reducing the complexity of catalyst system optimization.
Solution Approach 2:
The invention applies local quality by assigning specific functions to specific components: the metallocene compound controls polymerization activity and basic polymer structure, while the co-catalyst system specifically controls LCB content. This functional specialization allows precise control of LCB without requiring comprehensive re-optimization of the entire catalyst system.
3Manufacturing precision
If different metallocene compounds are used to achieve varying LCB levels, then the LCB content is controlled, but the consistency of other polymer characteristics deteriorates
Solution Approach 1:
The co-catalyst system serves as a universal component that can control LCB content across different metallocene compounds. By using the same metallocene compound with different co-catalysts, the invention achieves multi-functionality: the metallocene provides consistent polymerization activity and basic polymer structure, while the co-catalyst varies to achieve desired LCB levels, maintaining overall polymer property consistency.
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
This approach enables precise control of LCB content in ethylene polymers without altering the metallocene component, improving properties like tear resistance and melt strength by producing polymers with varying LCB levels tailored for specific applications.
Implementation Method 1
contacting a metallocene compound, an organoaluminum compound, a first (high LCB) activator-support, and a second (low LCB) activator-support to form a catalyst composition
Data Source
AI summary
Methods for controlling the long chain branch content of ethylene homopolymers and copolymers produced in a polymerization process include the steps of contacting a metallocene compound, an organoaluminum compound, a high LCB activator-support, and a low LCB activator-support to form a catalyst composition, contacting the catalyst composition with ethylene and an optional olefin comonomer in a polymerization reactor system under polymerization conditions to produce an ethylene polymer having a LCB content, and controlling the relative amount of the high LCB activator-support and the low LCB activator-support in the catalyst composition to adjust the LCB content of the ethylene polymer.